Wiring board and method of producing the same

ABSTRACT

A wiring board includes: wiring layers; insulating layers disposed between the wiring layers; and external connection pads respectively including surface plated layers, for connecting to an external circuit. In each of the external connection pads in one face of the wiring board, an outer peripheral edge of the external connection pad is retracted from an outer peripheral edge of the surface plated layer toward a center of the external connection pad.

This application claims priority from Japanese Patent Application No.2008-305154, filed on Nov. 28, 2008, the entire contents of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a wiring board and a method ofproducing the same, and more particularly to a wiring board of a type inwhich pads for mounting a semiconductor chip or the like are disposed onone face, and pads for connecting with another mounting board aredisposed on the other face.

DESCRIPTION OF RELATED ART

In a wiring board which is used, for example, in packaging of electroniccomponents such as a semiconductor chip, pads for mounting asemiconductor chip, an electronic component, or the like are disposed onone face, and pads for connecting with another mounting board aredisposed on the other face. In order to attain joining with solder bumpswhich are used for connections with a semiconductor chip or the like,and those with a mounting board, a surface plated layer is formed oneach surface of such external connection pads. A surface plated layer isformed by thinly plating nickel (Ni), gold (Au), and the like from theside of the pad.

FIG. 27 shows an example of an external connection pad in a wiring boardwhich is produced by a usual build-up technique. The external connectionpad 101 is formed on the outermost insulating layer 102 of the wiringboard, by a conductor material such as copper (Cu), and, at a positioncorresponding to the external connection pad 101, connected through avia 105 which is passed through an insulating layer 102, to a pad 104which is formed in one end of a lower wiring 103. A solder resist layer106 is disposed on the outermost surface of the board, and an openingportion 107 through which a part of the upper face of the externalconnection pad 101 is exposed is formed in the solder resist layer 106.A surface plated layer 108 is placed on the exposed upper face of theexternal connection pad 101.

As a method of producing a wiring board, Domestic Re-publication of PCTPatent Application No. 2003/039219 discloses in which a core board foralternately forming a wiring layer and an insulating layer on both thefront and rear faces of the wiring board by a build-up technique is notused, external connection pads are first formed together with surfaceplated layers on a support member such as a copper plate, a requirednumber of wiring layers and insulating layers are formed on the externalconnection pads by a build-up technique, external connection pads areformed on the opposite side, and thereafter the support member isremoved, thereby forming a wiring board.

FIG. 28 shows an example of an external connection pad (that isinitially formed on the support member) on one face of the wiring boardwhich is produced by the method. In the external connection pad 121, oneside is covered by a surface plated layer 122, and the surface of thesurface plated layer is exposed from that of the outermost insulatinglayer 123. The external connection pad 121 is connected through a via124 which is passed through the insulating layer 123, to a pad 126 whichis formed in one end of a lower wiring 125. An external connection padon the other face of the board is configured in the same as that whichhas been described with reference to FIG. 27.

In the external connection pad 101 of FIG. 27, the opening portion 107is formed in the solder resist layer 106 that is formed so as to coverthe whole face of the board after the formation of the pad, and a partof the pad is exposed for connection with a semiconductor chip or anexternal circuit. Therefore, the pad 101 must be formed larger than theopening portion 107 of the solder resist layer. This configurationhinders miniaturization of wirings.

Since the external connection pad 101 is formed in a large size, theamount of a resin which is between the pad 101 and the pad 104 of thelower wiring (specifically, the resin which is surrounded by verticalbroken lines A shown in FIG. 27, the lower face of the pad 101, theupper face of the pad 104, and the side face of the via 105) is large,and hence there is a possibility that the connection reliability of thevia is lowered by, for example, formation of a crack in a connectingportion between the pads and the via and due to stress caused by heatshrinkage of the resin.

In the case of the external connection pad 121 of FIG. 28, it ispossible to solve the above-discussed problems. However, the surfaceplated layer 122 and the pad 121 therebelow have the same size, andhence a crack 131 which is formed due to stress between the surfaceplated layer 122 and the insulating layer 123 easily propagates towardthe interior of the insulating layer 123 along the side face of the pad121, thereby producing breakage of the wiring or the like. Therefore,this disadvantage tends to cause the performance of the wiring board tobe degraded.

SUMMARY OF INVENTION

Illustrative aspects of the present invention provide a wiring board anda method of producing the same in which external connection pads that donot hinder miniaturization of wirings, that can maintain the connectionreliability of vias, and that hardly cause degradation of theperformance of the wiring board are formed in one face of the wiringboard.

According to a first aspect of the present invention, a wiring boardincludes: wiring layers; insulating layers disposed between the wiringlayers; and external connection pads respectively including surfaceplated layers, for connecting to an external circuit. In each of theexternal connection pads in one face of the wiring board, an outerperipheral edge of the external connection pad is retracted from anouter peripheral edge of the surface plated layer toward a center of theexternal connection pad.

Other aspects and advantages of the invention will be apparent from thefollowing description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an external connection pad which is in thewiring board of the present invention, and in which the outer peripheraledge of the external connection pads is retracted from the outerperipheral edge of a surface plated layer toward the center of theexternal connection pad.

FIG. 2 is a view illustrating a crack which is formed between thesurface plated layer and the insulating layer in the wiring board of thepresent invention.

FIGS. 3A to 3E are first views illustrating the production of a wiringboard of Example 1.

FIGS. 4A to 4D are second views illustrating the production of thewiring board of Example 1.

FIG. 5 is a view showing a wiring board of Examples 1 and 2 on which asemiconductor chip is mounted.

FIG. 6 is a view showing the wiring board of Examples 1 and 2 in which asemiconductor chip is mounted on a face opposite to the case of thewiring board of FIG. 5.

FIGS. 7A to 7D are first views illustrating the production of the wiringboard of Example 2.

FIGS. 8A to 8D are second views illustrating the production of thewiring board of Example 2.

FIGS. 9A to 9E are first views illustrating the production of a wiringboard of Example 3.

FIGS. 10A to 10D are second views illustrating the production of thewiring board of Example 3.

FIG. 11 is a view showing a wiring board of Examples 3 and 5 on which asemiconductor chip is mounted.

FIG. 12 is a view showing the wiring board of Examples 3 and 5 in whicha semiconductor chip is mounted on a face opposite to the case of thewiring board of FIG. 11.

FIGS. 13A to 13F are first views illustrating the production of a wiringboard of Example 4.

FIGS. 14A to 14D are second views illustrating a production of thewiring board of Example 4.

FIG. 15 is a view showing the wiring board of Example 4 on which asemiconductor chip is mounted.

FIG. 16 is a view showing the wiring board of Example 4 in which asemiconductor chip is mounted on a face opposite to the case of thewiring board of FIG. 15.

FIGS. 17A to 17F are first views illustrating a production of the wiringboard of Example 5.

FIGS. 18A to 18D are second views illustrating a production of thewiring board of Example 5.

FIGS. 19A to 19F are first views illustrating a production of a wiringboard of Example 6.

FIGS. 20A to 20D are second views illustrating a production of thewiring board of Example 6.

FIG. 21 is a view showing the wiring board of Example 6 on which asemiconductor chip is mounted.

FIG. 22 is a view showing the wiring board of Example 6 in which asemiconductor chip is mounted on a face opposite to the case of thewiring board of FIG. 21.

FIGS. 23A to 23F are first views illustrating a production of a wiringboard of Example 7.

FIGS. 24A to 24D are second views illustrating a production of thewiring board of Example 7.

FIG. 25 is a view showing the wiring board of Example 7 on which asemiconductor chip is mounted.

FIG. 26 is a view showing the wiring board of Example 7 in which asemiconductor chip is mounted on a face opposite to the case of thewiring board of FIG. 25.

FIG. 27 is a view illustrating an external connection pad in arelated-art wiring board which is produced by a build-up technique.

FIG. 28 is a view illustrating an external connection pad in anotherrelated-art wiring board.

FIG. 29 is a view illustrating a crack which is formed between a surfaceplated layer and an insulating layer in a pad portion shown in FIG. 28.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A wiring board of the present invention is characterized in that anouter peripheral edge of each of external connection pads in one face isretracted from an outer peripheral edge of a surface plated layer towardthe center of the external connection pad.

FIG. 1 shows an external connection pad 1. The pad 1 has a surfaceplated layer 2 on the side of connection to an external circuit. As anexample, each of the pad 1 and the surface plated layer 2 is formed in acircular shape from a planar view. A center of the surface plated layer2 coincides with a center of the pad 1. In the pad 1, an outerperipheral edge 1 a is retracted from an outer peripheral edge 2 a ofthe surface plated layer 2 toward the center of the pad 1, andpositioned inside the outer peripheral edge 2 a of the surface platedlayer 2. In order to attain the object of the present invention,preferably, the pad 1 is made as small as possible. However, the lowerlimit of the size depends mainly on the production accuracy which isrequired for ensuring joining of the pad 1 and a via 3 for connectingthe pad 1 to a wiring 4 in the board. By contrast, the size of thesurface plated layer 2 which is joined to the pad 1 depends on that of abump (not shown) which is to be connected. The actual size of the pad 1should be determined in view of these dependencies. In a standard wiringboard, for example, the horizontal distance (the length indicated by Din FIG. 1) between the outer peripheral edge 1 a of the pad 1 and theouter peripheral edge 2 a of the surface plated layer 2 may be set to beabout 0.1 to 5 μm, preferably, about 1 to 3 μm.

Referring to FIG. 1, the via 3 is connected to the wiring 4 through apad 5 which is at a position corresponding to the external connectionpad 1, and which is positioned in one end of the wiring 4. The externalconnection pad 1, the surface plated layer 2, the via 3, the wiring 4,and the pad 5 connected to the wiring 4 are in an insulating layer 7except the upper face of the surface plated layer 2.

In the related art which has been described with reference to FIG. 27,the size of the opening portion 107 of the solder resist layer 106 whichis connected to the pad 101 for connecting with an external circuitdefines that of the surface plated layer 108 which is positioned there,and depends on that of a bump to be connected. Because, after the solderresist layer 106 which covers the pad 101 is formed, the opening portion107 must be formed in the solder resist layer 101, the pad 101 must beformed to be larger than the opening portion 107 or larger than thesurface plated layer 108. In this case, the outer peripheral edge of thepad 101 is inevitably positioned outside that of the surface platedlayer 108.

In the present invention, by contrast, the outer peripheral edge 1 a ofthe external connection pad 1 is retracted from the outer peripheraledge 2 a of the surface plated layer 2 toward the center of the pad, andthe former is positioned inside the latter (FIG. 1). The retraction ofthe outer peripheral edge 1 a of the external connection pad 1 towardthe center of the pad enables the wirings of the wiring board of thepresent invention to be miniaturized, and reduces the amount of a resinwhich is between the external connection pad 1 and the pad 5 connectedto the inner wiring 4, i.e., a resin which is surrounded by verticalbroken lines B shown in FIG. 1, the lower face of the pad 1, the upperface of the pad 5, and the side face of the via 3, as compared with thecase of the related art which has been described with reference to FIG.27. Therefore, it is possible to maintain the connection reliability ofthe via against stress caused by heat shrinkage of the resin.

In the related art which has been described with reference to FIG. 28,the crack 131 which is formed due to stress between the surface platedlayer 122 and the insulating layer 123 easily propagates toward theinterior of the insulating layer 123 along the side face of the pad 121as shown in FIG. 29, and therefore there is a problem in that thepropagation easily causes the performance of the wiring board to bedegraded.

In the present invention, by contrast, a crack 9 which is formed betweenthe surface plated layer 2 and the insulating layer 7 propagates alongthe side face of the surface plated layer 2 and stops there as shown inFIG. 2, so that the crack does not penetrate very deeply into theinsulating layer 7. Therefore, the problem in that the performance ofthe wiring board is degraded is avoided.

In the present invention, the term “external circuit” means a circuitwhich is outside the wiring board, and to which the wiring board is tobe connected. For example, “external circuit” in the present inventionis a circuit of a semiconductor chip or another electronic componentwhich is to be mounted on the wiring board, that of a mounting board towhich a wiring board on which such a semiconductor chip and the like aremounted is to be connected, or the like.

The materials of the members constituting the wiring board of thepresent invention may be similar to those of equivalent members in ausual wiring board. As the material of the external connection pad, forexample, a usual wiring material such as copper (Cu) or a copper alloymay be used. As the material of the surface plated layer disposed on theexternal connection pad, (1) a combination of Ni and Au, (2) acombination of Ni, Pd, and Au, (3) Sn, (4) a combination of Sn and Ag,or the like may be used. In the case of the combination of (1), (2), or(4), plated layers are sequentially stacked so that the Au layer or theAg layer is exposed to the outside.

The wiring board of the present invention can be produced by a method inwhich external connection pads are first formed together with surfaceplated layers on a support member made of a metal such as a copper plateor a copper foil, required numbers of insulating layers and wiringlayers are formed on the external connection pads by a build-uptechnique, external connection pads are formed on the opposite side areformed, and thereafter the support member is removed. A process ofretracting the outer peripheral edge of each of the external connectionpads of one face of the wiring board from that of the surface platedlayer toward the center of the pad can be performed before the initialformation of the surface plated layer by a build-up technique.

In the thus produced wiring board of the present invention, the externalconnection pads which are initially formed on the support member arepads in each of which the outer peripheral edge is retracted from thatof the surface plated layer toward the center of the pad, and bycontrast the external connection pads on the opposite side (the finalpads formed by the build-up technique) are larger than the surfaceplated layer. Mainly, the former pads are used for mounting asemiconductor chip or another electronic component on the wiring board,and the latter pads are used for mounting the wiring board on a mountingboard. In some cases, nevertheless, the pads may be used in the oppositemanner.

EXAMPLES

Next, the present invention will be further described by way ofexamples. However, the present invention is not restricted to theexamples described below.

Example 1

In Example 1, a wiring board in which the surface of a surface platedlayer and that of a wiring board are in the same plane will be describedtogether with a method producing it.

As shown in FIG. 3A, a plate resist pattern 12 which will be used as amask pattern is formed on the surface of a Cu plate serving as a supportmember 11. In FIG. 3A, for the sake of simplicity, only the resistpattern 12 on one face of the support member 11 is shown. Actually, alsothe opposite face of the support member 11 is covered by a plate resistpattern. As the support member 11, other than a Cu plate, a Cu foil or aplate or foil of another metal or alloy which can be removed by a usualetchant may be used. As shown in FIG. 3B, surface plated layers 13 andexternal connection pads 14 are sequentially formed by electrolyticplating on the support member 11 which is exposed in bottom portions ofopening portions 12 a (FIG. 3A) (having a diameter of 100 μm) of theplate resist pattern 12. The electrolytic plating is performed byfeeding power from the support member 11. Here, each thickness of theexternal connection pads 14 is greater than each thickness of thesurface plated layers 13. Each of the surface plated layers 13 is formedby an Au layer and Ni layer respectively having thicknesses of 0.5 μmand 5 μm (the Au layer and the Ni layer are formed in this sequence).The external connection pads 14 are formed by Cu so as to have athickness of 10 μm.

Next, while using an etchant which dissolves only Cu, the externalconnection pads 14 are selectively etched so that the outer peripheraledges of the external connection pads 14 are made smaller by about 1 to3 μm than the outer peripheral edges of the surface plated layers 13(FIG. 3C). After etching, the plate resist pattern 12 is removed (FIG.3D), and then a resin film is laminated over the whole face so as tocover the pads 14, thereby forming an insulating layer 15 (FIG. 3E). Asthe resin film, a film of epoxy, polyimide, or the like may be used.

As shown in FIG. 4A, next, via holes 15 a are formed in the insulatinglayer 15 by laser processing. The diameter of each of the via holes 15 ais 60 μm in the surface of the insulating layer 15, and about 50 μm inthe bottom portion from which the pad 14 is exposed, so that the viahole 15 a is formed into a circular truncated cone-like shape in whichthe opening portion side has a larger diameter. Then, vias 16 aconnected to the pads 14, and a wiring pattern for a wiring layer 16 bconnected to the vias 16 a are formed (FIG. 4B). For example, the wiringlayer 16 b is formed by copper. In this process, for example, a usualmethod such as the semi-additive method can be used.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 15and wiring layers 16 b as shown in FIG. 4C, and the external connectionpads 17 (having a diameter of 200 to 1,000 μm) are formed together witha wiring pattern on the uppermost insulating layer 15. Then, a solderresist layer 18 having opening portions 18 a which are connected to thepads 17 is formed. Furthermore, surface plated layers 19 are formed byelectroless plating on the pads 17 which are exposed in the openingportions 18 a. In the surface plated layers 19, for example, a Ni layerand an Au later are formed in this order. Other words, the surfaceplated layers 19 are formed of the Ni layer and the Au layer so as toexpose the Au layer externally. Thereafter, the support member 11 isremoved by etching, thereby completing a wiring board 10 as shown inFIG. 4D. In the completed wiring board 10, the pads 14 in the face 10 afrom which the support member 11 is removed are used as pads forconnecting with a semiconductor chip or the like, and the pads 17 in theopposite face are used as pads for connecting with a mounting board.

FIG. 5 shows the wiring board 10 on which a semiconductor chip 21 ismounted. The semiconductor chip 21 is connected to the pads 14 of thewiring board 10 by solder joining members 22 which are formed byreflowing bumps that are previously disposed on the semiconductor chip21. The gap between the wiring board 10 and the semiconductor chip 21 isfilled with an underfill resin 23.

As shown in FIG. 6, the semiconductor chip 21 may be connected to thepads 17 in the face opposite to the face 10 a of the wiring board 10from which the support member 11 is removed. In this case, the pads 14in the face 10 a of the wiring board 10 from which the support member 11is removed are used as pads for connecting a mounting board (not shown).

Example 2

Hereinafter, a wiring board in which the surface of a surface platedlayer and that of a wiring board are in the same plane will be describedtogether with another method producing it.

As shown in FIG. 7A, a plate resist pattern 32 is formed on the surfaceof a Cu plate serving as a support member 31 (a resist layer (not shown)is formed also on the rear face of the support member 31). As thesupport member 31, other than a Cu plate, a Cu foil or a plate or foilof another metal or alloy which can be removed by a usual etchant may beused. As shown in FIG. 7B, surface plated layers 33 and externalconnection pads 34 are sequentially formed by electrolytic plating onthe support member 31 which is exposed in bottom portions of openingportions 32 a (FIG. 7A) (having a diameter of 100 μm) of the plateresist pattern 32. As each of the surface plated layers 33, an Au layerand Ni layer respectively having thicknesses of 0.5 μm and 5 μm areformed in this sequence. The external connection pads 34 are formed byNi so as to have a thickness of 10 μm.

Next, the plate resist pattern 32 is peeled off, and then the externalconnection pads 34 made of Ni are selectively etched so that the outerperipheral edges of the external connection pads 34 are made smaller byabout 1 to 3 μm than the outer peripheral edges of the plated layers 33(FIG. 7C). As shown in FIG. 7D, thereafter, a resin film is laminatedover the whole face so as to cover the external connection pads 34,thereby forming an insulating layer 35. In the formation of theinsulating layer 35, a resin film of epoxy, polyimide, or the like maybe used.

As shown in FIG. 8A, next, via holes 35 a are formed in the insulatinglayer 35 by laser processing. The diameter of each of the via holes 35 ais 60 μm in the surface of the insulating layer 35, and about 50 μm inthe bottom portion from which the pad 34 is exposed. Then, vias 36 aconnected to the pads 34, and a wiring layer 36 b connected to the viasare formed by, for example, the semi-additive method (FIG. 8B).

Then, the formation of an insulating layer, and that of vias and awiring layer are repeated to form predetermined numbers of insulatinglayers 35 and wiring layers 36 b as shown in FIG. 8C, and externalconnection pads 37 (having a diameter of 200 to 1,000 μm) are formedtogether with a wiring pattern on the uppermost insulating layer 35.Then, a solder resist layer 38 having opening portions 38 a which areconnected to the pads 37 is formed. Furthermore, surface plated layers39 are formed by electroless plating on the pads 37 which are exposed inthe opening portions 38 a. Thereafter, the support member 31 is removedby etching, thereby completing a wiring board 30 as shown in FIG. 8D. Inthe completed wiring board 30, the pads 34 in the face 30 a from whichthe support member 31 is removed are used as pads for connecting with asemiconductor chip or the like, and the pads 37 in the opposite face areused as pads for connecting with a mounting board. In this case, theconfiguration where a semiconductor chip is connected to the wiringboard 30 is identical with that in the case of the wiring board 10 ofExample 1, or as exemplarily shown in FIG. 5.

Similarly with the case of the wiring board 10 of Example 1, also in thewiring board 30 of Example 2, the semiconductor chip may be connected tothe pad 37 in the face of the wiring board 30 opposite to the face 30 afrom which the support member 31 is removed. In this case, as shown inFIG. 6, the pads 34 in the face 30 a of the wiring board 30 from whichthe support member 31 is removed are used as pads for connecting amounting board (not shown).

Example 3

Hereinafter, an example of a wiring board in which a surface platedlayer is positioned in a recess of the wiring board will be describedtogether with a method producing it. The materials and dimensions of themembers, the processing methods, and the like used in the followingexamples are identical with those described in Examples 1 and 2, unlessotherwise specified.

As shown in FIG. 9A, a plate resist pattern 42 having opening portions42 a is formed on the surface of a Cu plate serving as a support member41 (a resist layer (not shown) is formed also on the rear face of thesupport member 41). As shown in FIG. 9B, surface plated layers 43(formed by an Au layer and a Ni layer) and external connection pads 44made of Cu are sequentially formed by electrolytic plating on thesupport member 41 which is exposed in bottom portions of openingportions 42 a.

After the plate resist pattern 42 is removed (FIG. 9C), the Cu materialis selectively etched so that, as shown in FIG. 9D, the outer peripheraledges of the pads 44 are made smaller by about 1 to 3 μm than the outerperipheral edges of the surface plated layers 43, and a part of thesupport member 41 made of the Cu material is dissolved away by sideetching and undercut due to the mask effect of the surface plated layers43, so that peripheral edge portions of the surface plated layers 43 onthe side contacted with the support member 41 are exposed. Therefore,projections 41 a having a height of about 1 to 3 μm are formed on thesupport member 41, and the surface plated layers 43 and the pads 44 areplaced on the projections 41 a. After the etching, a resin film islaminated over the whole face so as to cover the pads 44, therebyforming an insulating layer 45 (FIG. 9E).

As shown in FIG. 10A, next, via holes 45 a are formed in the insulatinglayer 45 by laser processing. As shown in FIG. 10B, thereafter, vias 46a connected to the pads 44, and a wiring pattern for a wiring layer 46 bconnected to the vias 46 a are formed.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 45and wiring layers 46 b as shown in FIG. 10C, external connection pads 47are formed together with a wiring pattern on the uppermost insulatinglayer 45, and thereafter a solder resist layer 48 having openingportions 48 a which are connected to the pads 47 is formed. Next,surface plated layers 49 are formed by electroless plating on the pads47 which are exposed in the opening portions 48 a. Thereafter, thesupport member 41 is removed together with the projections 41 a byetching, thereby completing a wiring board 40 as shown in FIG. 10D. Inthe completed wiring board 40, the pads 44 in the face 40 a from whichthe support member 41 is removed are used as pads for connecting with asemiconductor chip or the like, and the pads 47 in the opposite face areused as pads for connecting with a mounting board.

In the wiring board 40 of Example 3, by the removal of the supportmember 41 by etching, recesses 45 b in which the opening portions on theside of the face 40 a have a larger diameter in conforming to the shapeof the projections 41 a of the support member 41 are formed in theinsulating layer 45 which has been contacted with the support member 41.Because of the recesses 45 b, in the case where a semiconductor chip isflip chip connected to the wiring board 40, when bumps of thesemiconductor chip are positioned in the recesses 45 b, the bumps can beeasily connected to the wiring board, and the positioning of the chipcan be facilitated. Moreover, the peripheral edge portions of thesurface plated layers 43 are covered by the insulating layer 45, andhence the adhesion strength of the surface plated layers 43 to thewiring board 40 is improved.

FIG. 11 shows the wiring board 40 on which the semiconductor chip 21 ismounted. The semiconductor chip 21 is connected to the pads 44positioned in the recesses 45 b (FIG. 10D) of the wiring board 40, bythe solder joining members 22 which are formed by reflowing bumps thatare previously disposed on the semiconductor chip 21. The gap betweenthe wiring board 40 and the semiconductor chip 21 is filled with theunderfill resin 23.

As shown in FIG. 12, the semiconductor chip 21 may be connected to thepads 47 in the face opposite to the face 40 a of the wiring board 40from which the support member 41 is removed. In this case, the pads 44in the face 40 a of the wiring board 40 from which the support member 41is removed are used as pads for connecting a mounting board (not shown).

Example 4

Hereinafter, another example of a wiring board in which a surface platedlayer is positioned in a recess of the wiring board will be describedtogether with a method producing it.

As shown in FIG. 13A, a plate resist pattern 52 having opening portions52 a is formed on the surface of a Cu plate serving as a support member51 (a resist layer (not shown) is formed also on the rear face of thesupport member 51). Sacrificial layers 51′ (having a thickness of 1 to30 μm) which are made of Cu of the same material as the support member51 are formed by electrolytic plating on the support member 51 which isexposed in bottom portions of opening portions 52 a (FIG. 13B). When thesupport member 51 is removed later, also the sacrificial layers 51′ areremoved together with the support member 51. Therefore, the sacrificiallayers 51′ are preferably made of the same material as the supportmember 51. As shown in FIG. 13C, thereafter, surface plated layers 53(formed by an Au layer and a Ni layer) and external connection pads 54made of Cu are formed similarly by electrolytic plating in a sequentialmanner.

Next, the outer peripheral edges of the pads 54 are made smaller byabout 1 to 3 μm than the outer peripheral edges of the surface platedlayers 53 as shown in FIG. 13D, by selective etching of Cu, and then theplate resist pattern 52 is removed (FIG. 13E). Thereafter, a resin filmis laminated over the whole face so as to cover the pads 54, therebyforming an insulating layer 55 (FIG. 13F).

As shown in FIG. 14A, next, via holes 55 a are formed in the insulatinglayer 55 by laser processing. As shown in FIG. 14B, thereafter, vias 56a connected to the pads 54, and a wiring pattern for a wiring layer 56 bconnected to the vias 56 a are formed.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 55and wiring layers 56 b as shown in FIG. 14C, external connection pads 57are formed together with a wiring pattern on the uppermost insulatinglayer 55, and thereafter a solder resist layer 58 having openingportions 58 a which are connected to the pads 57 is formed. Next,surface plated layers 59 are formed by electroless plating on the pads57 which are exposed in the opening portions 58 a. Thereafter, thesupport member 51 is removed together with the sacrificial layers 51′ byetching, thereby completing a wiring board 50 as shown in FIG. 14D. Inthe completed wiring board 50, the pads 54 in the face 50 a from whichthe support member 51 is removed are used as pads for connecting with asemiconductor chip or the like, and the pads 57 in the opposite face areused as pads for connecting with a mounting board.

In the wiring board 50 of Example 4, by the removal of the supportmember 51 by etching, recesses 55 b in which the opening portions on theside of the face 50 a have a larger diameter in conforming to the shapeof the sacrificial layers 51′ are formed in the insulating layer 55which has been contacted with the support member 51. Because of therecesses 55 b, in the case where a semiconductor chip is flip chipconnected to the wiring board, when bumps of the semiconductor chip arepositioned in the recesses 55 b, the bumps can be easily connected tothe wiring board, and the positioning of the chip can be facilitated.

FIG. 15 shows the wiring board 50 on which the semiconductor chip 21 ismounted. The semiconductor chip 21 is connected to the pads 54positioned in the recesses 55 b (FIG. 14D) of the wiring board 50, bythe solder joining members 22 which are formed by reflowing bumps thatare previously disposed on the semiconductor chip 21. The gap betweenthe wiring board 50 and the semiconductor chip 21 is filled with theunderfill resin 23.

As shown in FIG. 16, the semiconductor chip 21 may be connected to thepads 57 in the face opposite to the face 50 a of the wiring board 50from which the support member 51 is removed. In this case, the pads 54in the face 50 a of the wiring board 50 from which the support member 51is removed are used as pads for connecting a mounting board (not shown).

Example 5

Hereinafter, a further example of a wiring board in which a surfaceplated layer is positioned in a recess of the wiring board will bedescribed together with a method producing it.

As shown in FIG. 17A, a plate resist pattern 62 having opening portions62 a is formed on the surface of a Cu plate serving as a support member61 (a resist layer (not shown) is formed also on the rear face of thesupport member 61). Sacrificial layers 61′ (having a thickness of 1 to30 μm) which are made of Cu of the same material as the support member61 are formed by electrolytic plating on the support member 61 which isexposed in bottom portions of opening portions 62 a (FIG. 17B). As shownin FIG. 17C, thereafter, surface plated layers 63 (formed by an Au layerand a Ni layer) and external connection pads 64 made of Cu are formedsimilarly by electrolytic plating in a sequential manner.

After the plate resist pattern 62 is removed (FIG. 17D), the Cu materialis selectively etched so that, as shown in FIG. 17E, the outerperipheral edges of the pads 64 are made smaller by about 1 to 3 μm thanthe outer peripheral edges of the surface plated layers 63, and a partof the support member 61 made of the Cu material, and a part of thesacrificial layers 61′ are dissolved away by side etching and undercutdue to the mask effect of the surface plated layers 63, so thatperipheral edge portions of the surface plated layers 63 on the sidecontacted with the support member 61 are exposed. Therefore, projections61 a having a height of about 1 to 3 μm are formed on the support member61, and the sacrificial layers 61′, the surface plated layers 63, andthe pads 64 are placed on the projections 61 a. After the etching, aresin film is laminated over the whole face so as to cover the pads 64,thereby forming an insulating layer 65 (FIG. 17F).

As shown in FIG. 18A, next, via holes 65 a are formed in the insulatinglayer 65 by laser processing. As shown in FIG. 18B, thereafter, vias 66a connected to the pads 64, and a wiring pattern for a wiring layer 66 bconnected to the vias 66 a are formed.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 65and wiring layers 66 b as shown in FIG. 18C, external connection pads 67are formed together with a wiring pattern on the uppermost insulatinglayer 65, and thereafter a solder resist layer 68 having openingportions 68 a which are connected to the pads 67 is formed. Next,surface plated layers 69 are formed by electroless plating on the pads67 which are exposed in the opening portions 68 a. Thereafter, thesupport member 61 is removed together with the projections 61 a and thesacrificial layers 61′ by etching, thereby completing a wiring board 60as shown in FIG. 18D. In the completed wiring board 60, the pads 64 inthe face 60 a from which the support member 61 is removed are used aspads for connecting with a semiconductor chip or the like, and the pads67 in the opposite face are used as pads for connecting with a mountingboard.

In the wiring board 60 of Example 5, by the removal of the supportmember 61 by etching, recesses 65 b which conform to the shapes of theprojections 61 a of the support member 61 and the sacrificial layers 61′are formed in the insulating layer 65 which has been contacted with thesupport member 61. Because of the recesses 65 b, in the case where asemiconductor chip is flip chip connected to the wiring board 60, whenbumps of the semiconductor chip are positioned in the recesses 65 b, thebumps can be easily connected to the wiring board, and the positioningof the chip can be facilitated. Since also the sacrificial layers 61′ isremoved in the formation of the recesses 65 b by etching, deeperrecesses can be formed. Moreover, the peripheral edge portions of thesurface plated layers 63 are covered by the insulating layer 65, andhence the adhesion strength of the surface plated layers 63 to thewiring board 60 is improved.

The configuration of Example 5 where a semiconductor chip is connectedto the wiring board 60 is basically identical with that in the case ofthe wiring board 40 of Example 3, or as exemplarily shown in FIG. 11.Similarly with the case of the wiring board 40 of Example 3, also in thecase of the wiring board 60 of Example 5, the semiconductor chip may beconnected to the pads 67 in the face opposite to the face 60 a of thewiring board 60 from which the support member 61 is removed. In thiscase, as shown in FIG. 12, the pads 64 in the face 60 a of the wiringboard 60 from which the support member 61 is removed are used as padsfor connecting a mounting board (not shown).

Example 6

Hereinafter, an example of a wiring board in which a surface platedlayer is projected from the surface of the wiring board will bedescribed together with a method producing it.

As shown in FIG. 19A, a plate resist pattern 72 having opening portions72 a is formed on the surface of a Cu plate serving as a support member71 (a resist layer (not shown) is formed also on the rear face of thesupport member 71). The support member 71 is etched while using theresist pattern 72 as a mask, to form semispherical recesses 71 a in thesupport member 71 (FIG. 19B). As shown in FIG. 19C, then, surface platedlayers 73 (formed by an Au layer and a Ni layer) and external connectionpads 74 made of Cu are sequentially formed by electrolytic plating inthe recesses 71 a.

Next, the outer peripheral edges of the pads 74 are made smaller byabout 1 to 3 μm than the outer peripheral edges of the surface platedlayers 73 as shown in FIG. 19D, by selective etching of Cu, and then theplate resist pattern 72 is removed (FIG. 19E). Thereafter, a resin filmis laminated over the whole face so as to cover the pads 74, therebyforming an insulating layer 75 (FIG. 19F).

As shown in FIG. 20A, next, via holes 75 a are formed in the insulatinglayer 75 by laser processing. As shown in FIG. 20B, thereafter, vias 76a connected to the pads 74, and a wiring pattern for a wiring layer 76 bconnected to the vias 76 a are formed.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 75and wiring layers 76 b as shown in FIG. 20C, external connection pads 77are formed together with a wiring pattern on the uppermost insulatinglayer 75, and thereafter a solder resist layer 78 having openingportions 78 a which are connected to the pads 77 is formed. Next,surface plated layers 79 are formed by electroless plating on the pads77 which are exposed in the opening portions 78 a. Thereafter, thesupport member 71 is removed by etching, thereby completing a wiringboard 70 as shown in FIG. 20D. In the completed wiring board 70, thepads 74 in the face 70 a from which the support member 71 is removed areused as pads for connecting with a semiconductor chip or the like, andthe pads 77 in the opposite face are used as pads for connecting with amounting board.

FIG. 21 shows the wiring board 70 on which the semiconductor chip 21 ismounted. The semiconductor chip 21 is connected to the pads 74 of thewiring board 70, by the solder joining members 22 which are formed byreflowing bumps that are previously disposed on the semiconductor chip21. Since the pads 74 are projected, the connection can be suitablyperformed even when the solder joining members 22 are fine and have asmall diameter. The gap between the wiring board 70 and thesemiconductor chip 21 is filled with the underfill resin 23.

As shown in FIG. 22, the semiconductor chip 21 may be connected to thepads 77 in the face opposite to the face 70 a of the wiring board 70from which the support member 71 is removed. In this case, the pads 74in the face 70 a of the wiring board 70 from which the support member 71is removed are used as pads for connecting a mounting board (not shown).

Example 7

Hereinafter, another example of a wiring board in which a surface platedlayer is projected from the surface of the wiring board will bedescribed together with a method producing it.

As shown in FIG. 23A, a plate resist pattern 82 having opening portions82 a is formed on the surface of a Cu plate serving as a support member81 (a resist layer (not shown) is formed also on the rear face of thesupport member 81). The support member 81 is etched while using theresist pattern 82 as a mask, to form semispherical recesses 81 a in thesupport member 81 (FIG. 23B). As shown in FIG. 23C, then, surface platedlayers 83 (formed by an Au layer and a Ni layer) and external connectionpads 84 made of Cu are sequentially formed by electrolytic plating inthe recesses 81 a.

After the plate resist pattern 82 is removed (FIG. 23D), the Cu materialis selectively etched so that, as shown in FIG. 23E, the outerperipheral edges of the pads 84 are made smaller by about 1 to 3 μm, anda part of the support member 81 made of the Cu material is dissolvedaway by side etching and undercut by an etchant, so that peripheral edgeportions of the surface plated layers 83 on the side contacted with thesupport member 81 are exposed. Thereafter, a resin film is laminatedover the whole face so as to cover the pads 84, thereby forming aninsulating layer 85 (FIG. 23F).

As shown in FIG. 24A, next, via holes 85 a are formed in the insulatinglayer 85 by laser processing. As shown in FIG. 24B, thereafter, vias 86a connected to the pads 84, and a wiring pattern for a wiring layer 86 bconnected to the vias 86 a are formed.

The formation of an insulating layer, and that of vias and a wiringlayer are repeated to form predetermined numbers of insulating layers 85and wiring layers 86 b as shown in FIG. 24C, external connection pads 87are formed together with a wiring pattern on the uppermost insulatinglayer 85, and thereafter a solder resist layer 88 having openingportions 88 a which are connected to the pads 87 is formed. Next,surface plated layers 89 are formed by electroless plating on the pads87 which are exposed in the opening portions 88 a. Thereafter, thesupport member 81 is removed by etching, thereby completing a wiringboard 80 as shown in FIG. 24D. In the wiring board 80, the peripheraledge portions of the surface plated layers 83 are covered by theinsulating layer 85, and hence the adhesion strength of the surfaceplated layers 83 to the wiring board 80 is improved. In the wiring board80, moreover, the pads 84 in the face 80 a from which the support member81 is removed are used as pads for connecting with a semiconductor chipor the like, and the pads 87 in the opposite face are used as pads forconnecting with a mounting board.

FIG. 25 shows the wiring board 80 on which the semiconductor chip 21 ismounted. The semiconductor chip 21 is connected to the pads 84 of thewiring board 80, by the solder joining members 22 which are formed byreflowing bumps that are previously disposed on the semiconductor chip21. The gap between the wiring board 80 and the semiconductor chip 21 isfilled with the underfill resin 23.

As shown in FIG. 26, the semiconductor chip 21 may be connected to thepads 87 in the face opposite to the face 80 a of the wiring board 80from which the support member 81 is removed. In this case, the pads 84in the face 80 a of the wiring board 80 from which the support member 81is removed are used as pads for connecting a mounting board (not shown).

While the present inventive concept has been shown and described withreference to certain exemplary embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A wiring board comprising: wiring layers; insulating layers disposedbetween said wiring layers; and external connection pads respectivelyincluding surface plated layers, wherein, in each of said externalconnection pads in one face of said wiring board, an outer peripheraledge of said external connection pad is retracted from an outerperipheral edge of said surface plated layer toward a center of saidexternal connection pad.
 2. A wiring board according to claim 1, whereinsurfaces of said surface plated layers in said one face are positionedin a same plane as a surface of said wiring board.
 3. A wiring boardaccording to claim 1, wherein said surface plated layers in said oneface are positioned in recesses of a surface of said wiring board,respectively.
 4. A wiring board according to claim 1, wherein saidsurface plated layers in said one face are projected from a surface ofsaid wiring board.
 5. A wiring board according to claim 3, whereinperipheral edge portions of said surface plated layers in said one faceare covered by one of said insulating layers of said wiring board.
 6. Awiring board according to claim 4, wherein peripheral edge portions ofsaid surface plated layers are covered by one of said insulating layersof said wiring board.
 7. A wiring board according to claim 1, whereinsaid external connection pads in said one face are pads for mounting asemiconductor chip or another electronic component on said wiring board.8. A wiring board according to claim 1, wherein said external connectionpads in said one face are pads for mounting said wiring board on anotherboard.
 9. A method of producing a wiring board, comprising: (a)sequentially forming surface plated layers and external connection padson a support member; (b) retracting an outer peripheral edge of each ofsaid external connection pads from an outer peripheral edge ofcorresponding one of said surface plated layers toward a center of saidexternal connection pad; (c) forming wiring layers and insulating layerson said support member on which said external connection pads areformed; and (d) removing said support member.
 10. A method of producinga wiring board according to claim 9, wherein the formation of saidsurface plated layers and said external connection pads in said step (a)is performed by electrolytic plating using a mask pattern which isdisposed on said support member.
 11. A method of producing a wiringboard according to claim 10, wherein said step (b) is performed byselective etching which uses said mask pattern, and which is conductedon said external connection pads, and thereafter said mask pattern isremoved.
 12. A method of producing a wiring board according to claim 10,wherein, in said step (a), said external connection pads are formed by asame material as a material of said support member, said mask pattern isremoved after said step (a), and thereafter said step (b) is performedby selective etching which is conducted on said external connectionpads.
 13. A method of producing a wiring board according to claim 10,wherein, in said step (a), said external connection pads are formed by adifferent material from a material of said support member, said maskpattern is removed after said step (a), and thereafter said step (b) isperformed by selective etching which is conducted on said externalconnection pads.
 14. A method of producing a wiring board according toclaim 11, wherein, in said step (a), a sacrificial layer is formed onsaid support member, and thereafter said surface plated layers and saidexternal connection pads are formed.
 15. A method of producing a wiringboard according to claim 12, wherein, in said step (a), a sacrificiallayer is formed on said support member, and thereafter said surfaceplated layers and said external connection pads are formed.
 16. A methodof producing a wiring board according to claim 11, wherein, in said step(a), recesses are formed in said support member by etching which usessaid mask pattern, and thereafter said surface plated layers and saidexternal connection pads are formed.
 17. A method of producing a wiringboard according to claim 12, wherein, in said step (a), recesses areformed in said support member by etching which uses said mask pattern,and thereafter said surface plated layers and said external connectionpads are formed.